Experimental study on the dynamic shear modulus of foam lightweight soil based on resonant column tests
To gain a deeper undestanding of the dynamic characteristics of foam lightweight soil (FLS) subgrades in cold regions, resonant column tests were conducted to investigate the effects of wet density, clay content, and freeze–thaw cycles on the dynamic properties of FLS. The results indicate that the relationship between the dynamic shear modulus ratio ( G / G 0 ) and shear strain ( γ ) of FLS exhibits a consistent pattern: G / G 0 decreases slowly at low strain levels, with the rate of attenuation increasing significantly once a certain strain threshold is reached. Furthermore, the decay rate of G / G 0 with increasing γ gradually increases as the wet density of FLS decreases and the clay content increases. In this study, the G / G 0 – γ relationship substantially conforms to the Martin–Davidenkov model, which can be used to predict the variation trend of G / G 0 beyond the strain range of the resonant column tests, with the relevant formulas and parameter values ultimately provided. Based on the Hardin model, a multi-factor predictive model for the maximum shear modulus ( G 0 ) was developed, incorporating wet density, clay content, and freeze–thaw cycles, with its validity verified using a BP neural network algorithm. The research findings contribute to the accurate prediction of the dynamic response of FLS subgrades under varying conditions.